FIG. 6 is a drawing for explaining an outline of an oil passage in a control valve body of an automatic transmission for a vehicle in a related art. FIG. 6(a) is a sectional view schematically showing the oil passage in the control valve body. FIG. 6(b) is a sectional view taken along an A-A line of FIG. 6(a). FIG. 6(c) is an enlarged view of an area B in FIG. 6(a), for explaining vibration of a separate plate. FIG. 6(d) is an enlarged explanatory view of an orifice adjacent area of the separate plate.
The control valve body of the vehicle automatic transmission has a basic structure in which a separate plate 120 is sandwiched between valve body enclosures 100 and 110 which are coupled together. The valve body enclosures 100 and 110 have, on opposing surfaces thereof, channels 100a and 110a. Openings of these channels 100a and 110a are closed with the separate plate 120 sandwiched between the valve body enclosures 100 and 110, thereby separating the channels 100a and 110a and defining oil passages 101 and 102 in which working fluid flows.
The control valve body is provided with a solenoid, a spool (both not shown), etc. besides the oil passage inside the control valve body. The vehicle automatic transmission is configured so that the working fluid is supplied to a certain frictional engagement element by switching or changing the oil passage that provides the working fluid by driving the solenoid and the spool.
In the control valve body, there is a spot by which one side oil passage 101 and the other side oil passage 102 sandwiching the separate plate 120 communicate with each other through an orifice 121 that is provided at the separate plate 120. For instance, the working fluid in the one side oil passage 101 is pushed out to the other side oil passage 102 through the orifice 121 of this spot.
Here, the working fluid pushed out to the oil passage 102 through the orifice 121 moves along a center axis X of the orifice 121, and forms a flow F1 (see FIG. 6(c)) of the working fluid which flows on an extended line of the orifice 121 along the center axis X. Since there is a difference in a velocity of the flow between this working fluid flow F1 and a flow F2 of the working fluid positioned outside the extended line of the orifice 121, a vortex ring S caused by this flow velocity difference appears in the working fluid.
As shown in FIG. 6(b), since the orifice 121 is a small circular hole viewed from above, the vortex ring S formed in the oil passage 102 is formed cylindrically so as to surround the center axis X of the orifice 121. The vortex ring S formed in the oil passage 102 grows or develops while moving along the center axis X in a direction moving away from the orifice 121. Then, finally, a plurality of the vortex rings S continuously appear with the center axis X being a coaxial axis in a penetration direction (in an axial direction of the center axis X) of the orifice 121.
Here, the vortex ring S is a vortex that is different from a so-called Karman vortex. The vortex ring S is a vortex that is generated, caused by the orifice 121 of the separate plate 120, in the downstream side oil passage 102, and is a vortex of a jet passing through the orifice 121 of the control valve body.
With respect to the vortex ring S continuously appearing in the penetration direction of the orifice 121, a pressure of a segment Sd between contiguous vortex rings S and S becomes higher than that of a core Sc of the vortex ring S. Because of this, when the working fluid in the oil passage 101 is pushed out to the oil passage 102 through the orifice 121, fluctuation in up-and-down directions in the pressure adjacent to the orifice 121 in the oil passage 102 repeatedly occurs due to the vortex ring S continuously appearing.
Here, a section 120a of the separate plate 120, which is adjacent to the orifice 121, is not supported by being sandwiched between the valve body enclosures 100 and 110, thus rigidity of the section 120a in the penetration direction of the orifice 121 (in a direction orthogonal to the separate plate 120) is low. Therefore, when the pressure adjacent to the orifice 121 in the oil passage 102 fluctuates in the up-and-down directions, the section 120a of the separate plate 120, which is adjacent to the orifice 121, vibrates in the penetration direction of the orifice 121 (see an arrow a in the drawing) due to this pressure fluctuation, then a noise resulting from this vibration might be generated.
As suppressing measures of the noise resulting from the vibration of the separate plate 120, as shown in FIG. 6(d), it is said that forming a cone surface 122 at a downstream side opening edge of the orifice 121 formed at the separate plate 120, for instance, by coining process is effective. This technique has been disclosed, for instance, in a Patent Document 1.
According to this structure, as shown in FIG. 6(d), by slowing down a flow F1′ of the working fluid by the cone surface 122 and reducing a flow velocity difference between the working fluid flow F1′ and the working fluid flow F2, the vibration at the section 120a of the separate plate 120, which is adjacent to the orifice 121, is suppressed, then the noise resulting from this vibration is suppressed.
However, only a flow velocity suppressing effect by the cone surface 122 is not adequate for the noise suppression. The vibration at the section 120a of the separate plate 120, which is adjacent to the orifice 121, and the generation of the noise resulting from this vibration are not adequately suppressed, and thus a further measurement is required.